import java.util.Stack;

/**

* created by zl on 2019/3/28 10:44

*

* 只用一个stack实现，，其余算法都是要辅助栈

*/

public class simple_155_MinStack

{

int min = Integer.MAX_VALUE;

Stack<Integer> stack ;

public simple_155_MinStack()

{

stack = new Stack<Integer>();

}

public void push(int x)

{

// only push the old minimum value when the current

// minimum value changes after pushing the new value x

if(x <= min)

{

stack.push(min);

min=x;

}

stack.push(x);

}

public void pop()

{

// if pop operation could result in the changing of the current minimum value,

// pop twice and change the current minimum value to the last minimum value.

if(stack.pop() == min)

min=stack.pop();

}

public int top()

{

return stack.peek();

}

public int getMin()

{

return min;

}

}